1. Field of the Invention
This invention relates to a disc drive device for rotationally driving a disc-shaped recording medium.
2. Description of the Related Art
As a recording medium for recording information signals, a disc-shaped recording medium, abbreviated herein to a disc, having a disc-shaped substrate carrying a recording layer, is in widespread use.
This disc-shaped recording medium is housed in, for example, a cartridge to form a disc cartridge or is directly loaded on the disc drive device, without being housed in a cartridge. For this disc-shaped recording medium, information signals are recorded or read out by a head as the recording medium is run in rotation.
These discs of different diameter sizes have been proposed depending on the usage and application. Also, the disc cartridges of different sizes have been proposed depending on the size of the discs accommodated therein. The disc cartridge holding a small-sized disc is thinner in thickness than the disc cartridge holding a large-sized disc.
The disc drive device for rotationally driving these discs of different sizes is required to be able to cope with the discs of different sizes, that is to be compatible with respect to these discs.
However, with the discs of different sizes, the area of each disc held by the turntable of the disc drive device (holding area) is set to an optimum area depending on the disc size. The turntable of the disc drive device is also set to a diameter related to the size of the associated disc. In general, the larger the disc diameter, the broader is the holding area and the larger the size of the turntable.
Therefore, if a small-sized disc is to be run in rotation using a disc drive device associated with the large-size disc, the turntable encroaches into the disc recording area to decrease the recording capacity. Moreover, the head portion of the recording/reproducing apparatus tends to collide against the turntable.
On the other hand, if a large-sized disc is to be run in rotation using a disc drive device associated with the small-sized disc, the disc holding state is unstable to render it impossible to realize stable recording/reproduction.
Moreover, if, in case a disc is held in a cartridge and loaded as a disc cartridge in the disc drive device, the loaded cartridge differs in thickness, the disc height position in the disc drive device differs with the disc size to render it impossible to run the disc in rotation satisfactorily.